A fire in an empty furniture factory in eastern Zhejiang province went undetected for hours because the smoke was indistinguishable from the haze. In coastal Shandong province, most highways were closed for fear that low visibility would cause motorists to crash. And in Beijing, the local government urged residents to remain indoors and told construction sites to scale back activity.

"These are emergency measures that have the same economic impact as a strike or severe weather," said Louis Kuijs, a Hong Kong-based economist with the Royal Bank of Scotland and formerly of the World Bank. "They're very painful."

Residents in the capital have taken to mocking their famously filthy air and its attendant health hazards with the expression "Beijing cough." Meanwhile, Shanghai's Environmental Protection Bureau has introduced a cartoon mascot to communicate daily air quality on its website: a pig-tailed girl who bursts into tears when smog reaches hazardous levels.

But economists say China's smog is no joke. As air pollution continues to obscure China's cities, the cost to the nation in lost productivity and health problems is soaring. The World Bank estimates sickness and early death sapped China of $100 billion in 2009, or just under 3% of gross domestic product. China is now home to seven of the 10 most-polluted cities in the world, according to a report by the Asian Development Bank and Beijing's TsinghuaUniversity.

A study by Greenpeace and Peking University's School of Public Health put the cost of healthcare to treat pollution-related ailments in Beijing, Shanghai, Guangzhou and Xian at more than $1 billion last year.

Beijing resident Zhang Jian takes his 2-year-old son to a doctor regularly to treat the toddler's chronic sinus infection.

"It's definitely related to the pollution," said Zhang, 35, who wore a disposable mask at an overcrowded children's hospital recently. "My son snores and his nose is blocked constantly. It's a problem because he's too young to clear his nose like adults."

The doctor's visit and treatment cost Zhang about $320 — nearly a week's pay for the IT professional.

The Beijing government says it's considering a host of emergency measures to clear the air. Among them: limiting vehicle usage, spraying building sites to reduce dust and restricting outdoor barbecue grills.

Even China's next premier, Li Keqiang, weighed in recently on the issue. "This is a problem accumulated over a long period of time, and solving the problem will also require a long time. But we need to take action."

China's smog crisis is not unlike those experienced in London and Los Angeles in the 1950s. Public outcry ultimately led to cleaner air and tougher environmental regulations.

Environmental activists hope the same happens in China. The official response in recent weeks has raised optimism that authorities will begin addressing pollution more openly.

Until recently, state media was loathe to use the word "pollution," opting instead for the euphemism "fog."

But popular pressure is building, making it harder for policymakers to ignore the foul air in many of China's largest cities.

After the staggeringly bad bout of air pollution in the middle of this month, micro-bloggers took to posting pictures of themselves online wearing masks.

Some held handwritten signs that read, "I don't want to be a human vacuum cleaner."

The phrase became the top-trending topic on the Twitter-like Sina Weibo, attracting several million hits.

"Return my blue sky and white clouds," wrote a blogger named Xiao Yu. "If economic development needs to come with the price of such heavy pollution, I would rather go back to the 1980s."

China's economy has grown 30-fold since 1989, becoming the world's largest emitter of carbon dioxide in the process.

China has also emerged as the world's largest manufacturer of wind turbines and solar panels. The government aims to have renewable energy account for 9.5% of all power consumption by 2015.

Such is the contradictory nature of China's environmental policy. Plastic shopping bags are being phased out, solar water heaters abound and the country's northern provinces are planting 1.5 million square miles of new trees called the Green Wall of China.

At the same time, China remains highly dependent on coal to fuel its power plants. The dirty fossil fuel accounts for about 70% of China's energy production.

Compounding the problem is the nation's new love affair with the automobile. Nearly 20 million vehicles were sold here last year, more than anywhere else in the world.